1. Field of the Invention
The present invention relates to crystalline silicon plates, a process for growing crystalline silicon plates, a crystalline silicon plate-growth apparatus, and solar cell elements using crystalline silicon plates as substrates.
2. Related Art Statement
The crystalline silicon solar cell is produced by the four steps of preparing a raw silicon material, producing a substrate from the are silicon material, forming a cell structure on the substrate, and converting the cell structure into a module. The silicon substrate is ordinarily produced by the Czochralski process (CZ process: pulling-up process) (See "Cell Manual" published by Maruzen Co., Ltd.). Further, a lateral type crystal continuous growth apparatus has been known for growing silicon crystal plates for solar cells.
However, in such a lateral type crystal continuous growth apparatus, it was impossible to uniformly and continuously grow a crystalline silicon plate having an extremely small thickness. For example, a thickness of less than 200 .mu.m. On the other hand, according to the Czochralski process, a cylindrical silicon crystal may be grown, but then must be cut. Furthermore, it is known that a crystalline silicon plates can be made by growing a polycrystal body according to the casting process and cutting it. However, according to such growing methods, a large percentage of the silicon crystal which cut is thrown away. As a result, a lot of the material is wasted, resulting in a high crystal-growing production cost. Therefore, it is difficult to reduce production costs for the solar cell element. Since silicon is scarce as a natural source and its material cost is high. This has lead to increases in the production cost of silicon based solar cell elements.
In order to produce the solar cell element, a P-type or N-type diffusion area is formed at a surface of a crystalline silicone plate by diffusing a dopant element thereinto to obtain a P-N junction. However, such a diffusing process is complicated, which is a large factor to raise the production cost.